converted entity emailer models over to new entity event sources
subentity_kind -> sub_entity_kind
corrected the emailer migrations for entity events
added a function to convert events to emails
added more tests for checking group subscriptions and email conversions
more tests for converting events into emails
tested that email events are marked as seen when converted
tested unsubscription logic for converting emails
added celery tasks for converting events to emails
entity emailer uses the context loader from event sources now to load context information
entity emailer adds the entity emailer url to the context
updated to use new method in entity event
coverage
Merge branch 'develop' into feature/entity-event
Merge pull request #21 from wesleykendall/feature/entity-event

Emailer uses entity events